1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and a printer, and also to a cartridge.
2. Related Background Art
An image forming apparatus that has hitherto used an electrophotographic image forming process, involves adopting a process cartridge system, therein an electrophotographic photosensitive member and a process means acting on the electrophotographic photosensitive member are formed integrally into a cartridge which is set detachable from and attachable to a main body of the image forming apparatus. According to this process cartridge system, the user himself or herself is able to conduct maintenance of the apparatus without calling a service person, and therefore operability can be by far more enhanced than ever. This being the case, the process cartridge system is widely used in the image forming apparatus.
The image forming apparatus of this cartridge system requires a device for notifying the user of when the cartridge should be exchanged because the user himself or herself is to exchange the cartridge.
As a device for detecting a life-span of the cartridge, there has hitherto been proposed a method by which a non-volatile memory means such as an EEPROM is utilized for storing an integrated using quantity of the cartridge. Proposed in, for example, Japanese Patent Application Laid-Open No. 63-212956 is an electrophotographic image forming apparatus constructed such that a cartridge incorporates a memory classified as a non-volatile memory means as described above, a main body has a device for executing reading and writing processes from and to the memory, information on a life-span of the cartridge is calculated based on a content read from the memory and on an electrophotographic operation, and this item of information is written to the memory.
Proposed further in Japanese Patent Application Laid-Open No. 3-230172 is an image forming apparatus in which a non-volatile storage medium provided in an exchange unit stores characteristic information of the unit and a quantity with which the unit is used.
There arise, however, the following problems inherent in the above methods of detecting the life-span of the parts and detecting a quantity of the toners consumed.
According to the methods stated in Japanese Patent Application Laid-Open Nos. 63-212956 and 3-230172, the information for detecting the life-span of the photosensitive body involves the use of the number of prints with which the cartridge is used, and information on the integration of the number of rotations of the photosensitive drum. These items of information are comparatively well coincident with the life-spans of the respective parts constituting the cartridge, but insufficient in terms of accuracy for determining the life-span of the cartridge for the reason which follows. To be specific, the number of prints and the number of rotations of the photosensitive drum have a correlation with an abrasion/fatigue of the photosensitive drum, which is one of determinants of the life-span of the process cartridge. No consideration is, however, given to a quantity of disposal toners collected by the cleaner, which is another determinant of the life-span. Therefore, if a container becomes full of the disposal toners removed by the cleaners before reaching the life-span conditioned by the abrasion of the photosensitive drum, there must be caused critical damage to the main body of the apparatus, such as, e.g., a breakage of a drive gear due to an increase in torque of the process cartridge and a wide intra-machine scatter of the disposal toners when leaking out of the collecting container.
Moreover, the full storage of the disposal toners is detected by the main body of the apparatus, from which time the number of printable sheets is displayed, and, even in such a case, it is impossible to precisely display the number of remaining printable sheets, viz., how many sheets can be printed later on when the user detaches and attaches the process cartridge thereto or to a main body of other apparatus on such an occasion that the memory of the main body of the apparatus is stored with information showing the container becoming full of the disposal toners and information indicating the number of remaining printable sheets.